Upgrade NixOS to 25.11 and fix Jovian module organization

- Update flake inputs from 25.05 to 25.11 (nixpkgs, home-manager, nix-darwin)
- Remove Jovian compatibility shim that's no longer needed
- Move SteamOS configuration to only import in nix-deck machine
- Fixes jovian module not found error during nixos-rebuild

roles/desktop/default.nix

@@ -22,6 +22,5 @@ with lib;
     ./kde.nix
     ./programs.nix
     ./sddm.nix
-    ./steamos.nix
   ];
 }